This invention relates generally to vehicle suspension systems and more particularly to improvements in heavy duty suspensions of the type used on multiple axle over-the-road semi trailers.
In the past, semi trailer suspension systems have normally made use of four spring beams which function as leaf springs to provide at least some resiliency in the connection between the semi trailer body and axles. This type of suspension is rather stiff and can create problems if fragile cargo is being transported. Air cushion suspensions have been proposed and are advantageous in that they provide a softer ride and are less likely to damage the cargo. However, the air ride suspensions that have been proposed in the past are unduly expensive and require heavy components which have an adverse effect on fuel economy and hauling capacity.
The present invention is directed to an improved suspension system which makes use of air cushioning to achieve a soft ride without the cost and weight disadvantages that have plagued other air cushion suspension systems. In accordance with the invention, a heavy duty suspension system includes a pair of leaf spring beams for each axle, with the spring beams acting primarily to resist roll movement of the semi trailer. The spring beams make sliding contact in the hangers projecting from the frame of the suspension, and the axles are mounted near the centers of the spring beams by axle clamp assemblies. Transverse mounting tubes for air cushions are connected with the spring beams and receive the air cushions that provide cushioning that results in a soft ride. The spring beams on one side of the suspension system are pivoted at their back ends to transverse track rods which are pivoted at their opposite ends to rigid hanger brackets fixed to the frame. By virtue of this arrangement, the track rods are able to resist side to side loads and thus relieve the lateral loading on other components. This in turn allows lighter components to be used in the suspension because significant resistance to lateral loading is not required, and the overall weight of the suspension system is reduced accordingly.
The overall arrangement and combination of components provides the advantages of an air ride suspension and yet allows inexpensive and lightweight components to be used. As a consequence, the cost and weight problems traditionally associated with air ride suspensions are significantly reduced without sacrificing the desirable characteristics of an air ride suspension. At the same time, the construction of the suspension is such that it can be used on a wide variety of different types and sizes of over-the-road semi trailers.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.